A Wounded Ukraine Volunteer Lies in a Donetsk Prison—Where the Jailer Is Russian

DONETSK, Ukraine—Oleg Mamiyev, a Russian citizen with a beard and a lazy eye, descended a crooked flight of stairs into a basement on a rebel base here and unlocked a chain-link trapdoor to show off a prisoner.

Sitting on a cot that barely fit into his dark nook, the prisoner, Maxim Kucheryavy, was obviously hungry and in pain. A Ukrainian volunteer who wanted to fight pro-Russian insurgents, Mr. Kucheryavy said he had been shot in both legs at point-blank range while unarmed and already in detention. Bandaged and...